Inhibition of Pitting Corrosion of Some Austenitic Stainless Steel Samples in 2.5 M Nacl Solution by 3- Amino-1, 2, 4-Triazole

Abstract

The effect of addition of 3-AMINO-1,2,4-TRIAZOLE (ATA) on general and pitting corrosion of three Egyptian austenitic stainless steel samples, namely SS 304L (0.09 Mo), SS 304H (0.43 Mo) and SS 304H (1.15 Mo) in aerated 2.5 M NaCl solution was investigated. The measurements were carried out using potentiodynamic polarization and the Tafel lines methods. The influence of temperature on the inhibition properties of ATA was investigated. The results indicate that ATA is a good inhibitor for the samples under investigation in 2.5 M NaCl solutions. In addition, the inhibition efficiency η% increases with the inhibitor concentration while it decreases with increasing temperature. Moreover, addition of ATA to 2.5 M NaCl solution leads to a shift of the pitting potential towards the noble direction accounting for increased resistance to pitting attack. The inhibitive properties of the ATA were explained on the bases of its adsorption on the stainless steel samples and formation of adsorbed barrier layer, which resist the penetration power of Cl- ion and consequently decreases the rate of pitting corrosion. The adsorption of the inhibitor obeys a Temkin adsorption isotherm. Examination of polarization curves indicates that ATA acts as a mixed-type inhibitor.